This invention relates to an optical pickup for use in an optical disc driver such as a DVD player and, in particular, to an optical pickup which has a two wavelength laser for emitting two laser beams with different wavelengths.
As is well known in the art, a DVD (Digital Versatile or video Disc) player can plays not only a DVD but also a CD (Compact Disc). To permit playing both of the DVD and the CD, the DVD player has a special optical pickup with a special structure. The special optical pickup has two laser diodes to alternatively emit a first reading laser beam for the DVD or a second reading laser beam for the CD. The first reading laser beam is different from the second reading in wavelength. That is, the first reading beam has a shorter wavelength of about 650 nm while the second reading laser beam has a longer wavelength of about 780 nm. The special optical pickup is called two-wavelength correspondence type optical pickup.
A conventional two-wavelength correspondence type optical pickup comprises the first and the second laser diodes as mentioned above. The first and the second laser diodes are apart from each other and produce the first and the second reading laser beams, respectively. The first laser diode is called a DVD-LD while the second diode is called a CD-LD.
The optical pickup further comprises an optical system to lead the first laser beam from the first laser diode to an optical disc loaded in an optical disc player to which the optical pickup is attacked. The optical system also leads the second laser beam from the second laser diode to the optical disc. In addition, the optical system leads a reflected light beam reflected from the optical disc to a photo detector.
The conventional optical pickup needs two gratings and two polarizing beam splitters to correspond to two of the laser diodes in the optical system, because the laser diodes are relatively distant from each other. Accordingly, the conventional optical pickup has a problem that it has a large number of components and a complicated structure.